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When i feed seaweed all the fish get excited. My chromis and damsel especially just like to nip at it, but my hippo tang, although occasionally will eat it, usually is too shy to eat any. Anyway, to answer your question, I usually let it sit 2 or 3 minutes after no fish are showing interest, then i take it out.

I'd leave it in for at least a few hours to let everyone try it. Once your fish figure out it's food and you figure out how much of it to feed, it becomes easier to add an amount that you dont have to remove. Some fishes just don't like it though. My anthia have zero interest in attacking the sheet like the others but will take the occasional bite of a particle floating by

Don't forget you can cut the sheets to fit the size you need. No need putting a whole sheet in your tank for a couple of fish.

if you have it on a feeding clip the fish might find it strange and be hesitant to feed from it. Try putting it on a small piece of live rock with a rubber band to get them use to eating it. Once they eat it well then move it to the clip. This is how I started feeding it and now my fish devour it when I place it in the aquarium.
On another note, dont know how much of it your flame hawk will eat of it since they are stricktly carnivores. However, I had a pair of blue throat triggers that would destroy the seaweed strips and they are mainly carnivores as well.
Anyhow, good luck.

if you have it on a feeding clip the fish might find it strange and be hesitant to feed from it. Try putting it on a small piece of live rock with a rubber band to get them use to eating it. Once they eat it well then move it to the clip. This is how I started feeding it and now my fish devour it when I place it in the aquarium.

This has worked well for me, too. While the fish are getting used to eating the seaweed off the rocks, it would be a good idea to leave the empty clip in the tank at all times so they can get used to it being there. That way when you start to put the seaweed into the clip, they will be used to the clip already and won't shy away from it. After they get used to eating off the clip, you can remove it when you remove the seaweed.

Also my tangs and angels are the ones interested the most, none of my other fish seem overly interested.

I know its an old thread, and prolly a dumb question, but why is it a bad thing to leave the strips in the tank? I just tried the rock and rubber band trick for my blenny but it just seems to attract the shrimp and crabs. Might have to move it to a clip for it to last longer, but curious why I should only leave it for an hour or so.

It gets kind of nasty. Sheets of it also can break free and clog your overflow. I don't know about an hour, though. I try to only put in as much as they'll eat in a reasonable amount of time and usually don't need to worry about taking it out.